A descendant of an illustrious line of rabbis, Rav Slostowski received s’micha at the age of 17 and become a great gadol serving congregations in Poland, including teaching in the rabbinical seminary in Lodz. He became an authority on kashrut. He was invited to Israel by former Israeli Chief Rabbi, Rav Abraham Isaac Kook, where he was appointed Secretary to the Chief Rabbinate of Jerusalem.

After Rav Kook’s death in 1935, Slostowski moved to Tel Aviv and taught Talmud. Slostowski had a miraculous encounter while reading the New Testament in Hebrew that convinced him that Yeshua was the Jewish Messiah. He tried to keep his conviction quiet, but within two months he could do so no longer, and openly confessed Yeshua as the Messiah and resigned from his position in Tel Aviv. Soon afterward he was pelted with rocks and hospitalized. But he was undeterred in his faith. He continued to publicly proclaim that Yeshua is the Messiah despite constant persecution.